2015 Volume 2015 Issue 60 Pages 1-6
Heat-resistant stainless steel with excellent spring properties at high temperature was developed for exhaust gasket. Recently, the temperature of the automotive exhaust system parts has been rising. The press-formed bead for sealing on the gasket undergoes elastic deformation while pressed, and the repulsive force of the bead prevents the exhaust gas leak. At high temperature the strength of the steel decreases, and the repulsive force of the bead becomes weak. Therefore, it is difficult to prevent the exhaust gas leak. The developed steel is austenitic stainless steel which does not transform at high temperature, and the strength is improved through cold rolling and nitrogen solution. In addition, the drastic hardness decrease is prevented as a result of the retardation of the austenite recovery and recrystallization by the nitride particles which are formed at high temperature. Furthermore, the particles contribute precipitation hardening. The developed steel shows the hardness exceeding 400HV after aging at 600℃ for 400 hours.